The technical scope of the invention is that of embrittlement devices for a mechanical element, notably embrittlement devices used in automobile safety systems.
A device allowing an automobile vehicle brake pedal to be separated from its support pin by pyrotechnic means is known notably by patent DE19515852.
This system implements explosive bolts that, when ignited further to the detection of a shock, release the pedal from its support thus avoiding the serious injuries generally sustained to the legs and ankles of the driver in the event of a frontal collision as a result of the pedal.
The major drawback to such a device lies in the event of the inadvertent ignition of the explosive bolts, the brake pedal becomes entirely useless, seriously prejudicing the operating safety of the vehicle.
Patent DE19617372 describes an analogous device in which a pyrotechnic system ensures the fracturing of the connection between a brake pedal and the rod of the master cylinder or between the brake pedal and its hinge. After such a device has been activated no braking capability remains whatsoever.
Various mechanical systems fitted with embrittlement means are known elsewhere, for example, the stages of a booster rocket that must separate in flight, the grappling ropes of a parachute supporting a load and that must be released immediately, or the steering column of a vehicle that must be moved away from the driver in the event of an accident.
Patent U.S. Pat. No. 5,314,206 describes a safety device for automobile vehicle seats. This device comprises a piston that is displaced by drive means when the belt is attached by a passenger and that ensures the reinforcement of the seat and/or its sliding rail link.
In any event, providing a pre-embrittled area in the design itself prejudices the mechanical strength of the device, and thus its operational safety.
Therefore, the solution involving deliberate fracturing when needed (more often than not by pyrotechnic means) is preferred over that involving embrittlement. However, inadvertent ignition deprives the element of its normal operating capacities and prejudices its safety.
The aim of the invention is to propose an embrittlement device for a swivel pin of an automobile pedal that does not suffer from such drawbacks.
Thus, the embrittlement device according to the invention is of a structure such that, even in the event of the inadvertent activation of the embrittlement, the pedal remains operational to a certain degree.
The subject of the invention is thus an embrittlement device for a swivel pin of an automobile pedal, such device being characterised in that the pin incorporates at least one incipient fracture and at least one reinforcement means at right angles to the incipient fracture and strengthening the pin, the reinforcement means being able to be displaced under the action of drive means to take up a position at a distance from the incipient fracture thereby ensuring the embrittlement of the pin.
According to a particular embodiment, the incipient fracture is made in the form of a reduction of the shearable surface, the reinforcement means being placed at right angles to the incipient fracture and thus enabling the shearable surface to be increased.
According to another embodiment, the reinforcement means can comprise means ensuring their connection in rotation with the pin on the one hand and with the incipient fracture on the other thereby ensuring a reinforcement in torsion of the pin.
Advantageously, the drive means comprise a pyrotechnic gas generator.
The pin can be a hollow rod incorporating at least one groove forming the incipient fracture and the reinforcement means can be constituted by at least one piston able to be displaced by the gas pressure.
According to another characteristic, the piston can be held axially in place by a shearable lock.
According to a particular embodiment, the hollow rod can incorporate two grooves constituting incipient fractures, and two reinforcement means, first reinforcement means constituted by a first piston and second reinforcement means constituted by a second hollow piston, the second piston pressing on the fist piston such as to be able to push it axially.
The second piston can be obturated by a sealing fail receiving the gas pressure and able to fracture over a certain pressure rate.
The pistons will advantageously press against one another via matching conical surfaces.
The piston can incorporate a shoulder co-operating at the end of its stroke with an abutment integral with the rod.
The pin can allow the automobile pedal to swivel with respect to a fork joint, the incipient fractures being located on either side of the wings of the fork joint.